Conventional full aperture can ends include a score that extends about the major area of the end's center panel and defines a removable panel. A tab is attached to the removable panel by a rivet. The tab heel is lifted initially to rupture the score, and then the tab is pulled to propagate the score until the removable panel is fully detached from the remainder of the end. Typically, full aperture opening ends are seamed onto food can bodies by conventional means.
Full aperture food can ends are also typically designed to allow full product release of the foodstuff contained within the food can. Often, this foodstuff is packed under slight negative pressure. In applications in which the food can is under positive internal pressure, the internal pressures are relatively low and because the pressure's primary purpose is to maintain the structural rigidity of the food can, which is often relatively “thin-walled”.
The internal pressure in conventional beverage cans, such as for carbonated soft drinks or beer, typically is much higher than the internal pressures in food cans, resulting in concerns related to “blow-off” of the ends upon opening or when subjected to adverse handling. For these reasons, commercial beverage cans have ends defining a restricted aperture, which can be safely opened by a consumer.
U.S. Pat. No. 5,711,448, assigned to Reynolds Metals Company, describes a conventional “large opening end” (that is, and end having a large opening). The patent describes “standard size opening” of 0.5 square inches and a “larger opening” of 0.5 to 0.75 square inches, each of which represents a relatively small fraction of the center panel.
Full aperture beverage can ends have been sold in the past but had safety problems and have been withdrawn from the market. ‘Spiral scored’ ends were produced for Sapporo beer, where the can end was vented in its centre and then the score propagated to the edge of the can end panel and the around the periphery thereof. Venting was critical because the end was relatively large, 66 mm diameter with a 52 mm centre panel size. If the end was opened without being vented, the panel could explode and missile towards the consumer. Thus a vent was used to provide safe venting and release the internal pressure in the can before opening. However the resulting spiral geometry of the opened end panel was dangerous having several long exposed cut edges and for this reason, this can end configuration was withdrawn.